Non-herbal tea consumption and ovarian cancer risk: a systematic review and meta-analysis of observational epidemiologic studies with indirect comparison and dose–response analysis

Abstract

Ovarian cancer (OC) accounts for 4% of female malignancies worldwide, and its prognosis is unfavorable. Currently available epidemiologic data suggest that non-herbal tea consumption may reduce OC risk, but these evidences are inconsistent. A comprehensive literature search for observational epidemiologic studies reporting associations between non-herbal tea consumption and OC risk was conducted in electronic databases. A random-effects model was used to synthesize effect measures in binary meta-analysis, and adjusted indirect comparison was used to compare whether there was a difference in effects between green tea (GT) and black tea (BT). Both linear and non-linear models were used to explore the dose-response relationship. Fourteen studies were included, and we obtained an inverse and significant pooled estimate in binary meta-analysis [risk ratio (RR)pool = 0.76, 95% confidence interval (CI) 0.61-0.95, PCochran < 0.001, I2 = 81.5%]. No publication bias was identified in binary meta-analysis. In binary meta-analysis stratified by tea types, we observed a significant association for GT (RRpool = 0.64, 95% CI 0.45-0.90, PCochran = 0.071, I2 = 53.6%), but not BT (RRpool = 0.85, 95% CI 0.65-1.12, PCochran = 0.007, I2 = 65.9%). Indirect comparison, which treated BT as the reference, showed an inverse but non-significant association (RRGT versus BT = 0.74, 95% CI 0.48-1.15). Both linear and non-linear models found that OC risk decreased as the consumption levels of total non-herbal tea increased. However, the dose-response relationship was stronger for GT when compared with BT. Our results suggest that non-herbal tea, especially GT, is associated with a reduced risk of OC. Future studies should explore biochemical evidence regarding the variation in chemopreventive effects between different types of non-herbal tea.

Tea Consumption and Health Outcomes: Umbrella Review of Meta‐Analyses of Observational Studies in Humans

“…One of the most prominent associations identified in the current umbrella review was that between tea consumption and diverse cancers; beneficial associations of tea consumption with gastric cancer, oral cancer, lung cancer, biliary tract cancer, thyroid cancer, ovarian cancer, leukemia, and glioma, and of green tea consumption with esophageal cancer and endometrial cancer we observed, although most of these had substantial heterogeneity that might not be readily explained by the epidemiological design, sex, or other important determinants for decreasing the risk of developing cancer. Interestingly, in most cohort and case‐control studies, cancer risk reduction was more frequently observed with green tea consumption.…”

“…In separate meta‐analyses, high consumption of tea was related to a reduced risk of biliary tract cancer, oral cancer, leukemia, thyroid cancer, lung cancer, and glioma . Considering the different types of tea, high consumption of green tea was associated with a reduced risk of liver cancer, ovarian cancer, endometrial cancer and esophageal cancer . Black tea consumption was associated with a lower risk of lung cancer.…”

Green tea and cancer and cardiometabolic diseases: a review of the current epidemiological evidence

“…A 2020 meta-analysis on green tea and breast cancer including 16 studies reported a pooled relative risks of 0.86 (95% CI: 0.75-0.99) [34]. Among reproductive organ-related cancers, meta-analyses on endometrial cancer [78] and ovarian cancer reported inverse associations RR = 0.89 (95% CI 0.84-0.94) and RR = 0.64 (95% CI 0.45-0.90), respectively [76]. An inverse association was also found for lung cancer OR = 0.69 (95% CI 0.48-0.82) [58], non-Hodgkins lymphoma RR = 0.61 (95% CI 0.38-0.99) [62] and oral cancer RR = 0.85 (95% CI 0.75-0.93) [64].…”

“…Table 2 reports results from meta-analyses on green tea and cardiovascular-related outcomes [14,21,22,[84][85][86][87]. Three 2 [13,14,22,26,34,40,45,54,58,62,64,65,69,76,78]. Note: Colorectal, lung and pancreatic cancer risk reported as Odds Ratios.…”

Tea consumption and breast cancer risk in a cohort of women with family history of breast cancer

“…Many types of organic chemical compounds are found in black and green tea, including multiple types of natural polyphenols . These chemicals may have anti‐tumorigenic properties . For instance, in vitro , clinical and epidemiologic studies suggest that (−)‐epigallocatechin‐3‐gallate (EGCG), the main polyphenol in green and black tea, may be beneficial for cancer prevention .…”